The invention relates to puncturing devices for blood vessels having an ultrasound probe for Doppler-effect-based location of the blood vessel, with a guide duct for a puncturing needle, through which duct on entry into the body the needle axis can be moved at least approximately coaxially relative to the beam transmitted by the probe, and sterile coverings for such puncturing devices. The ultrasound probe in such a device has a transmitter/receiver system by means of which ultrasound can be irradiated into the body and a signal from the partly reflected beam can be recorded. Due to the Doppler effect, reflection by the flowing blood leads to a frequency shift from which an acoustic and/or optical signal can be obtained. By seeking a maximum for such a signal it is possible to find the point of penetration for the puncturing needle.
Devices of this type are known, for example, from Swiss patent specification 676 787 (=P. 6297). The transmitter/receiver system is so constructed that a guide duct for the needle runs through the acoustic resonator. This design is disadvantageous because puncturing must be performed under sterile conditions and because the required gas sterilization of the ultrasound probe is very time-consuming. In a simpler ultrasound probe without an integrated guide duct sterility can be achieved with a sterile covering intended for use once only (see for example EP-A 0 104 618). In these simpler probes, however, the needles cannot run coaxial with the ultrasound beam transmitted.